Polyurethane foams modified with nonionic surfactants

ABSTRACT

A polyurethane composition for the production of single-component polyurethane foams on dry or wet substrates, wherein the composition is the reaction product of a polyol with a molar excess of difunctional or polyfunctional isocyanates and wherein 10% to 80% by weight of the polyol has been replaced by a nonionic surfactant containing at least one hydroxyl group.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to new polyurethane compositions modified withhydrophilic surfactants containing isocyanate-reactive functional groupsfor the production of fine-cell homogeneous polyurethane foams.

DISCUSSION OF RELATED ART Prior Art

Polyurethane foams, more especially so-called one-component polyurethanefoams, are known for example from Ullmanns Enzyklopadie der technischenChemie, 4th Edition, Vol. 19, pages 317 et seq., Verlag Chemie,Weinheim. The foams in question are mixtures of isocyanate-terminatedreaction products of polyols with difunctional or polyfunctionalisocyanates, catalysts to accelerate the reaction, viscosity-reducingagents, blowing agents and other auxiliaries which--protected againstmoisture--are marketed in pressurized containers. When they are releasedfrom the pressurized containers, the mixtures foam through evaporationof the blowing agent and cure under the effect of moisture from thesurrounding environment or from the atmosphere. Polyurethane foams areused, for example, for insulating domestic appliances, as an insulatingmaterial and for filling joints with foam in the building industry andas insulating materials.

They essentially contain polyols bearing several OH groups in themolecule, difunctional or polyfunctional isocyanates, blowing agents,flame-proofing agents and auxiliaries, such as catalysts andstabilizers.

The polyols used may be any of the polyether or polyester polyolstypically used in polyurethane chemistry. A review of possible polyolscan be found in Ullmanns Enzyklopadie der technischen Chemie, 4thEdition, Vol. 19, pages 304-5, Verlag Chemie, Weinheim. The productionof inexpensive oleochemical polyols from renewable raw materials andtheir use for this purpose is also known, cf. German patent applicationsDE-A1 36 26 223 and DE-A1 41 28 649. The first application claimsprepolymers based on oleochemical polyols which are obtained by ringopening of epoxidized triglycerides with alcohols and subsequent partialtransesterification. The second application describes thelithium-salt-catalyzed ring opening of epoxides with nucleophiles, suchas alcohols, optionally in conjunction with subsequenttransesterification of the reaction products with other non-epoxidizedtriglycerides.

Hitherto, chlorofluorocarbons (CFC's) have often been used as blowingagents. On account of ecological objections to these compounds whichdamage the ozone layer, so-called partly halogenated hydrocarbons(HCFC's) which are less damaging to the ozone layer, for exampledifluorochloromethane, difluorochloroethane, dichlorofluoroethane ortetrafluoroethane, have recently been used to an increasing extent asblowing agents. It is also known that fluorine-containing blowing agentsneed not be used at all, being replaced for example by dimethyl ether,propane or isobutane.

The use of more highly fluorinated or CFC-free blowing agents oroleochemical polyols, which is actually desirable from the ecologicalpoint of view, results in hydrophobicization of the polyurethanecompositions. As a result, the water which is absolutely essential forthe crosslinking and curing of the polyurethane compositions to formfoams is unable adequately to penetrate through the foam. This resultsin the formation of voids in the foam and in unwanted shrinkage of thefoam after setting. To avoid this, both the substrate and the foamitself have to be thoroughly moistened during processing of the foams.Voids occur in greater numbers when the polyurethane foams are appliedto dry substrates.

The formation of voids and shrinkage are technically undesirable andcomplicate or prevent application of the ecologically more favorablepolyurethane foams.

Accordingly, the problem addressed by the present invention was toprovide polyurethane foams, more especially based on oleochemicalpolyols and/or free from CFC-containing blowing agents, which would givefine-cell, homogeneous and substantially void-free foams withoutmoistening of the substrate and/or the foam.

Another problem addressed by the invention was to improve thepermeability of polyurethane foams to water and water vapor.

In addition, the stability of the polyurethane compositions packed inpressurized containers against precipitation, above all at lowtemperatures, would remain guaranteed.

DESCRIPTION OF THE INVENTION

According to the invention, the solution to this problem ischaracterized in that the polyols used for production are partlyreplaced by hydrophilic surfactants containing isocyanate-reactivefunctional groups.

Accordingly, the present invention relates to polyurethane compositionsfor the production of one-component polyurethane foams containingreaction products of polyols with a molar excess of difunctional orpolyfunctional isocyanates, characterized in that 10 to 80% by weight ofthe polyols are replaced by nonionic surfactants containing at least onehydroxyl group.

Nonionic Surfactants

Surfactants in the context of the present invention are compounds whichconsist of one or more hydrophobic groups and one or more nonionichydrophilic groups.

The hydrophobic groups are preferably optionally substituted hydrocarbonradicals. Polyethylene oxide or polyglycerol groups are mentioned asexamples of nonionic hydrophilic groups.

Suitable surfactants are those which, in addition to the hydrophilicgroup, contain an isocyanate-reactive functional group such as, forexample, fatty alcohol ethoxylates, alkylphenol ethoxylates, fatty acidamide ethoxylates, fatty acid amine ethoxylates, alkoxylatedOH-functional triglycerides, alk(en)yl oligoglycosides, fatty acidglucamides or partial esters of polymerized glycerol, i.e. compoundswhich can be covalently incorporated in the polyurethane.

Particularly suitable surfactants are those which contain several ofthese functional groups in the molecule, such as for example ethoxylatedcastor oil containing 20 to 400% by weight and preferably 40 to 200% byweight of EO, based on non-ethoxylated castor oil, or epoxidized soybeanoil ring-opened with alcohols or carboxylic acids which, after ringopening, is reacted with alkylene oxides, preferably ethylene oxide, toa content of 20 to 400% by weight and preferably 40 to 200% by weight ofalkylene oxide, based on the non-alkoxylated starting product.

A surfactant produced as described in German application DE-A1 39 23 394from epoxidized soybean oil ring-opened with fatty acid by subsequentreaction with ethylene oxide to an ethylene oxide content of 20 to 400%by weight and preferably 40 to 200% by weight, based on thenon-ethoxylated starting product, is most particularly suitable.

The hydroxyl values of the surfactants according to the invention are inthe range from 10 to 200 and preferably in the range from 30 to 100.

The compounds mentioned are used in quantities of 10 to 80% by weightand preferably in quantities of 20 to 50% by weight, based on thepolyol, for the replacement.

Another advantage of the last of the above-mentioned surfactantsaccording to the invention is that, surprisingly, they do notcrystallize at room temperature despite their high ethylene oxidecontent. Accordingly, no unwanted precipitations occur in the reactionproducts produced from them with diisocyanates, even at lowtemperatures.

The other components of the polyurethane foams will now be described.

Polyols

The polyols used are typical polyethers or polyesters which aredescribed, for example, in Ullmanns Enzyklopadie der technischen Chemie,4th Edition, Vol. 19, pages 304 to 305, Verlag Chemie, Weinheim. Inaddition, oleochemical polyols obtainable by reaction of epoxidizedtriglycerides with alcohols and, optionally, subsequenttransesterification of the reaction products on their own or with moreadded non-epoxidized triglyceride, are preferably used. Oleochemicalpolyols from the transesterification of polyfunctional polyols, such asthe adduct of glycerol with ethylene oxide or polymerized glycerol withtriglycerides, for example rapeseed oil, may also be used. Castor oil isanother suitable oleochemical polyol. The polyols have OH values of 50to 400 and preferably 100 to 300.

Isocyanates

Suitable difunctional or polyfunctional isocyanates are any of theproducts known to the expert which are typically used in polyurethanechemistry and which are described, for example, in Ullmanns Enzyklopadieder technischen Chemie, 4th Edition, Vol. 19, pages 303 to 304, VerlagChemie, Weinheim. Aromatic difunctional or polyfunctional isocyanatesare preferably used, diphenyl methane diisocyanate and/or the technicalqualitities of these diisocyanates containing molecules of highfunctionality being particularly preferred.

Auxiliaries

The blowing agents used are preferably HCFC's, such asdifluorochloromethane, difluorochloroethane, dichlorofluoroethane ortetrafluoroethane, or CFC-free blowing agents, such as dimethyl ether,propane or isobutane. However, CFC-containing blowing agents may also beused for the purposes of the invention although they are not preferred.

The polyurethane foams may contain other compounds, such asflameproofing agents, for example the tris-(chloroalkyl)-phosphates oraryl phosphates known from the prior art. The quantity in which theflameproofing agents are used is in the range from 8 to 15% by weight,based on the mixture as a whole. Suitable catalysts for accelerating thereaction are, for example, the tertiary amines known to the expert, forexample 2,2'-dimorpholinodiethyl ether. Silicone oils, optionally evenmodified silicone oils, may be used as stabilizers.

Production and Application

The polyurethane compositions according to the invention are produced bymixing the polyols with the modifying nonionic hydrophilic surfactant,the difunctional or polyfunctional isocyanate, the blowing agent, theflameproofing agent, the catalyst and optionally the stabilizer andpacking the resulting mixture in a pressurized container equipped with aspray valve.

When the pressurized mixture issues from the valve, a polyurethane foamis formed in the usual way and may be used, for example, for fillingjoints with foam, for insulation and the like.

COMMERCIAL APPLICATIONS

The polyurethane compositions according to the invention may be usedabove all in the building industry for the production of fine-cell,homogeneous, void-free or substantially void-free polyurethane foams ondry substrates without any need to moisten the foams.

The polyurethane compositions packed in pressurized containers arestable against precipitation during storage at low temperatures.

EXAMPLES

All quantities are expressed as percentages by weight, unless otherwiseindicated.

General procedure:

A polyurethane composition was prepared from the following ingredients:

    ______________________________________                                        19.7 pbw  of an oleochemical polyol prepared by ring                                    opening of epoxidized soybean oil with methanol                               and subsequent partial transesterification,                                   OHV = 180                                                           34.3 pbw  of Desmodur ® VKS, 31% NCO content                              24 pbw    of trichloropropyl phosphate                                        19.6 pbw  of a blowing agent of C.sub.2 H.sub.3 CIF.sub.2 + CHCIF.sub.2       1.6 pbw   of Dabco ® DC 190                                               0.8 pbw   of dimorpholinodiethyl ether                                        100 pbw   of polyurethane composition                                         ______________________________________                                    

DABCO DC 190 is a silicone surfactant manufactured by Dow Corning.Desmodur VKS is a polymeric isocyanate manufactured by Bayer AG.

The following nonionic hydrophilic surfactants were used:

Surfactant 1: ethoxylated castor oil containing 65% by weight ofethylene oxide

Surfactant 2: epoxidized soybean oil ring-opened with a mixture of C₆₋₁₂fatty acids and subsequently reacted with ethylene oxide to an ethyleneoxide content of 150% by weight, OH value=54.7.

Performance test:

The one-component polyurethane mixture was sprayed from pressurizedcontainers into 40 mm wide and 400 mm long joints. Dry cellulose andcellulose soaked with water were used as the substrates. The quality ofthe foams was evaluated after curing. The polyurethane strands were thencut up in order to reveal any voids.

    ______________________________________                                        Moist substrate:                                                              Example No.                                                                            1 (Comp.)   2           3                                            ______________________________________                                        Basic polyol                                                                           100%        70%         70%                                          Surfactant 1                                                                            --         30%          --                                          Surfactant 2                                                                            --          --         30%                                          Foam volume                                                                            Good        Good        Very good                                    Foam structure                                                                         Inhomogeneous                                                                             Partly inhomo-                                                                            Homogen-                                                          geneous     eous                                         Void formation                                                                         Slight      Slight      Very slight                                  Dimensional                                                                             6% By volume                                                                              3% By volume                                                                              1% By volume                                stability                                                                     (shrinkage)                                                                   ______________________________________                                        Dry substrate                                                                 Example No.                                                                            4 (Comp.)   5           6                                            ______________________________________                                        Basic polyol                                                                           100%        70%         70%                                          Surfactant 1                                                                            --         30%          --                                          Surfactant 2                                                                            --          --         30%                                          Foam volume                                                                            Poor        Good        Very good                                    Foam structure                                                                         Very inhomoge-                                                                            Partly inhomo-                                                                            Homogen-                                              neous       geneous     eous                                         Void formation                                                                         Frequent    Slight      Very slight                                  Dimensional                                                                             10% By volume                                                                             3% By volume                                                                              1% By volume                                stability                                                                     (shrinkage)                                                                   ______________________________________                                    

What is claimed is:
 1. A polyurethane composition for the production ofsingle-component polyurethane foams on dry or wet substrates, saidcomposition comprising the reaction product of a polyol with a molarexcess of difunctional or polyfunctional isocyanates wherein 10% to 80%by weight of said polyol has been replaced by a nonionic surfactantconsisting essentially of epoxidized soybean oil ring-opened withalcohols or carboxylic acids which after ring opening has been reactedwith an alkylene oxide to a content of 20% to 400% by weight of alkyleneoxide, based on non-alkoxylated soybean oil.
 2. A polyurethanecomposition as in claim 1 wherein said polyol comprises an oleochemicalpolyol obtained by ring-opening of epoxidized soybean oil with analcohol, and optionally, by subsequent transesterification.
 3. Apolyurethane composition as in claim 1 wherein said isocyanates comprisearomatic difunctional or polyfunctional isocyanates.
 4. A polyurethanecomposition as in claim 1 wherein said nonionic surfactant comprises thereaction product of the ring-opening of an epoxidized soybean oil withfatty acids reacted with ethylene oxide up to a content of 40% to 400%by weight, based on the weight of the non-alkoxylated ring-openingproduct.
 5. The process of producing a fine-cell, homogeneoussingle-component polyurethane foam on a dry or wet substrate comprisingapplying to said substrate a polyurethane composition comprising thereaction product of a polyol with a molar excess of difunctional orpolyfunctional isocyanates wherein 10% to 80% by weight of said polyolhas been replaced by a nonionic surfactant consisting essentially ofepoxidized soybean oil ring-opened with alcohols or carboxylic acidswhich after ring opening has been reacted with alkoxylene oxide to acontent of 20% to 400% by weight of alkylene oxide based onnon-alkoxylated soybean oil.
 6. A process as in claim 5 wherein saidpolyol comprises an oleochemical polyol obtained by ring-opening ofepoxidized soybean oil with an alcohol, and optionally, by subsequenttransesterification.
 7. A process as in claim 5 wherein said isocyanatescomprise aromatic difunctional or polyfunctional isocyanates.
 8. Aprocess as in claim 5 wherein said nonionic surfactant comprises thereaction product of the ring-opening of an epoxidized soybean oil withfatty acids reacted with ethylene oxide up to a content of 40% to 400%by weight, based on the weight of the non-alkoxylated ring-openingproduct.